1. 168.1 Hz
To find the apparent frequency heard by the driver in the car, we can use the formula for the Doppler effect:
where
f is the original sound of the horn
v is the speed of sound
is the velocity of the observer (the driver and the car), which is positive if the observer is moving towards the source and negative if it is moving away
is the velocity of the sound source (the train), which is positive if the source is moving away from the observer and negative otherwise
In this problem we have, according to the sign convention used:
Substituting, we find:
2.
The speed of light can be calculated as
where
d is the distance travelled
t is the time taken
In this problem:
is the total distance travelled by the laser beam (twice the distance between the Earth and the Moon)
t = 2.60 s is the time taken
Substituting in the formula,
In order to measure the resistance in the circuit, we need to know the voltage V and the current I in the circuit, this way we can calculate the resistance using the formula:
In order to calculate the current, we can use an amperemeter that must be in series with the circuit, this way it will not affect the circuit.
And in order to calculate the voltage, we can use a voltmeter that must be in parallel with the resistance, this way it will not affect the circuit.
The correct option that shows an amperemeter in series and a voltmeter in parallel is the fourth option.